Secondary seal



21, 1969 J. H. MCBRIEN ET AL 3,422,981

SECONDARY SEAL Filed April 18, 1967 Sheet of 2- INVENTORS ATTORNEY Jan. 21, 1969 Filed April 18, 1967 J. H. M BRIEN ET AL SECONDARY SEAL Sheet g of 2 [NV EN TOR S BYW ATTORNEY United States Patent 4 Claims ABSTRACT OF THE DISCLOSURE A floating t-ank roof having a secondary seal engaging the wall of the tank and supported on the primary seal means through an adapter which is fastened to the primary seal means, and which has an enlarged portion fitting within an enlarged portion of a slot in the secondary seal, and a removable filler strip for urging the slot into close engagement with the adapter.

Cross references to related applications This application discloses in part subject matter disclosed in patent application Ser. No. 526,293, filed Feb. 9, 1966, and assigned to the assignee of the present application, and also discloses in part subject matter disclosed in United States Patent No. 3,275,183 issued Sept. 27, 1966, to the same assignee as a result of the filing of application Ser. No. 343,660, filed Feb. 10,1964.

Background of the invention Field of the invention.This invention relates to storage tanks, such as for oil and oil products and the like, of the type having a floating roof or covering that floats on the liquid stored in the tank so that the roof rises and falls with the liquid level, and more particularly it relates to improved means for providing a seal 'between the periphery of the roof and the wall of the tank in which the roof is used.

Description of the prior art.In tanks with floating roofs a problem is encountered in maintaining an effective seal between the edge of the floating roof and the wall of the tank. Necessarily the roof is spaced inwardly of the wall of the tank so as to leave an annular space therebetween. It has previously been the practice to provide a primary seal which includes guide shoes which are attached to the floating roof and are resiliently biased against the wall of the tank, and which also includes a flexible sheet member extending from the guide shoes to the tank roof to provide means for preventing foreign material from falling through the annular space into the oil or oil products stored below the roof. For example, one such structure is shown in US. Patent No. 2,478,422. To further insure against leakage of rainwater and the like past the primary seal and the guide shoes into the oil or the like in the tank below the floating roof, more recently a secondary seal of resilient material, such as rubber, extending between the guide shoes and the wall of the tank had been used. Such secondary seals are shown, for example, in US. Patents 2,973,113, 3,106,309, 2,568,728, 2,897,998, and 3,167,206.

Due to various irregularities which are often found on the inside surfaces of tank walls, it is often diflicult to maintain a seal with the tank wall. One of the problems encountered is that projections on the tank wall, such as, for example, welding beads, may, upon downward move- 3,422,981 Patented Jan. 21, 1969 "ice ment of the tank roof, engage the secondary seal and cause it to be disengaged from the guide shoes so that the seal no longer performs satisfactorily.

Summary of the invention According to the present invention, difiiculties previously encountered are solved by providing an adapter means which positions the secondary seal so as to reduce the likelihood of engagement by projections from the tank wall and further provides retention means for resisting disengagement of the secondary seal. According to the preferred embodiment of the invention, means are provided for greatly facilitating the utilization of the retention means provided. The combination provided insures retention of the secondary seal in engagement with the guide shoes of the primary seal under all conditions of operation and avoids difliculties previously encountered in the secondary seal coming loose from the guide shoes or being pushed away from the wall of the tank so that the seal is lost.

Brief description of the drawings FIGURE 1 is a fragmentary sectional view showing one embodiment of an installation according to this invention;

FIGURE 2 is an enlarged sectional view of a portion of the structure shown in FIGURE 1 showing the seal member in vertical cross-section;

FIGURE 3 is a cross-sectional view of the flexible member alone of the assembly shown in FIGURE 1;

FIGURE 4 is a view similar to FIGURE 2 but showing another embodiment of the invention;

FIGURE 5 is a sectional view similar to FIGURE 2 but taken at a different place along the length of the seal member; and

FIGURE 6 is an isometric view of the embodiment of spring finger shown in FIGURE 5.

Description 0 the preferred embodiments FIGURE 1 depicts a cylindrical wall 10 of a conventional oil storage tank. The floating roof 12 of the tank is a hollow 'body having a relatively short height and having a diameter somewhat smaller than the inside diameter of the tank. It will be appreciated that such tanks are often 50 to feet or more in diameter. In the embodiment shown the floating roof is provided with an upstanding wall 14 around its circumference to retain on the roof any foreign materials which may fall into the open top of the tank. The wall 14 has at its upper end an inturned flange 16 which provides means to attach to the floating roof at flexible primary seal member 20. The primary seal is supported at its outer edge by a segmented support ring 22, each segment of which support ring is attached to a segmental guide shoe 24. The guide shoes and the support rings are made in short arcuate sections, as is well known in the art but not shown in the drawing, extending around the circumference of the tank. Each of the guide shoes is supported by and interconnected with the floating roof by means of the hanger structure indicated generally at 26. The hanger structure includes an appropriate lever and weight arrangement to hold the shoes in contact with the inner surface of the tank side wall as the floating roof rises and falls in accordance with changes in the amount of liquid stored in the tank. Such structure is well known in the art and forms no part of the present invention and therefore it is not necessary to describe it in detail here.

The guide shoes are provided at their upper edges with inturned flanges 28 which form an acute angle with the wall of the tank. In the past it has been known to engage the inturned flanges 28 with an annular flexible secondary seal member, as shown for example in the aforesaid Patent No. 3,167,206. However, it has been found that in many instances it is impossible to attach a secondary seal in the manner described in said patent. For example, in many cases the flange 28 is very short, as shown in FIG- URES 2 and herein, so that a full engagement of the secondary seal member cannot be achieved. In other instances horizontal welds 30 extend beyond the surface of the tank wall so that, upon downward movement of the floating roof, the secondary seal member engages the weld and is pushed off of the flange 28.

Therefore in accordance with the present invention adapter means 32 is provided for engagement by the secondary seal.

In the embodiment shown in FIGURES 1, 2 and 5 the adapter member comprises a plurality of elongate strips which may for example be made up of extruded aluminum and cut into sections equivalent to or less than the length of the shoe sections. Thus, adapter strips are fastened to the inturned flange 28 of each shoe as by means of screws 34. The adapter strip is provided with an enlarged thickness portion 36 on one edge for engagement in a corresponding slot 38 in the secondary seal member 40.

The seal member 40 comprises a relatively thickened adapter engaging portion 42, a relatively thinned intermediate web portion 44 and a thickened wall engaging outer edge 46. The wall engaging portion 46 is provided with a tapered sealing lip 48 which is adapted to sealingly engage the wall of the tank. As best seen in FIGURE 3, in its normal condition (prior to installation) the relatively thickened adapter engaging portion 42 is angularly disposed at an obtuse angle with the relatively thinned portion 44. Thus, in its installed position, the slot 38 extends upwardly and radially inwardly of the tank. An annular groove 50 in the side of the thickened portion 42 is provided for receiving a locking strip 52. The groove also forms a reduced wall thickness between the groove and the enlarged portion 54 of the slot 38 so that when the locking strip 52 is not in place the thickened portion 42 may be bent easily to allow insertion of the adapter 32 so that its thickened portion 36 fits within the enlarged space 54 in the slot. Once the two enlarged portions are engaged the slot may be closed again and the locking or filler strip 52 may be inserted into the groove 50 to hold the slot in tight engagement with the adapter so that retention of the enlarged portion 36 of the adapter within the enlarged portion 54 of the slot is assured.

At the sides of the thinned portion 44 of the seal there are provided facing grooves 56 and 58 in which a plurality of stiffening members 60 are received. As shown, the stiffening members are provided at each end with lips 62 which engage corresponding recesses within the grooves 56 and 58 to retain the stiffening members in position. stiffening members may, for example, be made of a spring bronze or stainless steel.

In the embodiment shown, means are also provided for insuring that the sealing lips 48 ride over imperfections on the tank walls 10, as for example weld beads 30. Such means comprise resilient finger members 64, shown in detail in FIGURE 6, which include a curved wall engaging portion 66, a handle portion 68 and a locking arm 70. As may be seen in FIGURE 5, the curved portion 66 is inserted through a hole 72 which may be drilled or otherwise formed in the thickened portion 46 substantially parallel to the groove 56, the curved portion 66 being pushed through the hole until the locking arm 70 engages the recess at the bottom of the groove 56. The finger member 64 also may be made of bronze or stainless steel spring material.

The secondary seal member of this invention is preferable made of a resilient plastic material such as a synthetic or natural rubber which is preferably resistant to both hydrocarbons and water. Normally the filter strip 52 is of substantially the same material.

In assembly of the structure of this invention, bolt holes are usually drilled or punched along the flanges 28 of the guide shoes to correspond with holes or slots which are formed in the adapter strips 32. The adapter strips are then bolted on. The elongate seal member is then installed in comparatively long sections, e.g. 10-20 feet, on the adapter strips so as to form an annular seal extending all the way around the tank. The filler strips 52 are inserted to secure the seal member onto the adapter strips. The finger members 64 are then inserted into the holes 72 provided therefor and finally stiifeners 60 are put into place intermediate the finger members. It has been found that good results are obtained if stiffeners approximately 2 inches wide are used, spaced two inches apart, so that one finger member is used every 4 inches around the circumference.

It will be appreciated that with certain types of floating tank roofs it may be desirable to use a different form of adapter member. One example of such different form is shown in FIGURE 4. Here a clamp member 70 is utilized to hold the fabric portion 20 of the primary seal on to the shoe 24. An adapter member 72 is fastened to the clamp 70 as by means of bolts 74. The adapter extends upwardly from the clamp and then has an outwardly extending portion 76 followed by an upwardly and inwardly extending portion 78 which is enlarged at 80 at its extreme upper end. Thus, this adapter serves to position the flexible seal member 40 relatively closely to the wall 10 of the tank so that the sealing lip 48 thereof may adequately engage the wall, yet maintains the portion 42 of,the seal member at a desired distance away from the wall to insure that it will not contact the wall.

It will be seen that the structure provided by this invention insures that the seal member will not be disengaged from the upper edge of the tank roof, by providing means which maintain all of the seal member out of contact with the wall except the sealing edge itself, and further by means which insure retention of the engagement between the seal member and the elements forming the upper edge of the floating tank roof.

We claim:

1. In an open top container for holding fluid, having a floating roof therein, a primary seal having a plurality of shoes supported in contact with the inside surface of the vertical wall of the container, and a secondary seal supported at the top edges of the plurality of shoes and sealingly engaging said inside surface, said secondary seal comprising an annular flexible member having two portions axially disposed relative to each other, the radial cross sections of said portions being angularly disposed relative to each other, one of said portions extending upwardly and radially outwardly for sealingly engaging said inside surface, and the other of said portions being thickened and having an annular slot therein extending upwardly and radially inwardly,

the improvement which comprises an annular adapter for fastening to said top edges,

an enlarged thickness portion on said adapter positioned within said slot, and having a thickness greater than the width of said slot,

a corresponding enlarged space in said slot receiving said enlarged thickness portion, an annular groove in the thickened section of the secondary seal positioned to form a reduced thickness portion between the groove and the slot, whereby a portion of the thickened section can be bent to open up the slot so that the enlarged thickness portion of the adapter can be inserted into the slot,

and a filler strip engageable with said groove to urge said portion of the thickened section in a direction to close said slot to closely engage the adapter.

2. In a secondary seal for use with a floating roof in an open top tank by afiixture to the top edges of a plurality of shoes of the primary seal of said roof comprising an annular flexible member having two portions axial- 1y disposed relative to each other, the radial cross section of said portions being angularly disposed relative to each other, one of said portions extending upwardly and radially outwardly for sealing contacting the inside of the wall of the tank and the other of said portions being thickened and having an annular slot therein extending upwardly and radially inwardly,

the improvement which comprises an annular adapter for fastening to said top edges and having a portion engageable in said slot,

an annular groove on one face of said thickened portion forming a reduced wall thickness portion between the groove and the bottom of the slot,

a filler strip adapted to be inserted in said groove to force the sides of the slot into engagement with the adapter,

and cooperating retention means comprising corresponding enlarged portions on said adapter and in said slot to prevent the secondary seal from being pulled off the adapter.

3. In a secondary seal for use with a floating roof in an open top tank by affixture to the top edges of a plurality of shoes of the primary seal of said roof comprising annular resilient means having a first portion adapted to engage the inside of the wall of the tank and a second portion having an annular slot therein for engagement with said shoes,

the improvement which comprises an annular web on the top edge of said shoes, said web being positioned for engagement'in said slot,

an enlarged thickness portion on said web positioned to be received within said slot and having a thickness greater than the width of the slot,

a corresponding enlarged space in said slot positioned to receive said enlarged thickness portion of said web,

an annular groove positioned to form a reduced thickness portion between the groove and the slot, whereby a part of the second portion of the resilientmeans can be bent t open up the slot so that the enlarged thickness portion of the web can be inserted into the slot, and

a filler strip engageable with said groove to urge said part in a direction to close said slot to closely engage said web. 4. In a secondary seal for use with a floating roof in an open top tank by affixture to the top edges of a plurality of shoes of the primary seal of said roof comprising annular resilient means having a first portion adapted to engage the inside of the wall of the tank and a second portion having an annular slot therein for engagement with said shoes,

the improvement which comprises an annular adapter strip adapted to be fastened to said top edges and positioned for engagement in said slot,

an enlarged thickness portion on said strip positioned to be received within said slot and having a thickness greater than the width of the slot,

and a corresponding enlarged space in said slot positioned to receive said enlarged thickness portion of said adapter strip,

an annular groove positioned to form a reduced thickness portion between the groove and the slot, whereby a part of the second portion of the annular resilient means can be bent to open up the slot so that the enlarged thickness portion of the web can be inserted into the slot, and

a filler strip engageable with said groove to urge said part in a direction to close said slot to closely engage said web.

References Cited UNITED STATES PATENTS 2,354,629 7/1944 Wiggins 220-26 2,568,728 9/1951 Goldsby et a1 22026 2,897,998 8/1959 Ulm 220-26 2,973,113 2/1961 Fino 22026 3,106,309 10/1963 Nelson et a1. 22026 3,167,206 1/1965 Nelson 220 -26 3,275,183 9/1966 Challenger 22026 FOREIGN PATENTS 468,711 7/ 1937 Great Britain.

MARTHA L. RICE, Primary Examiner.

JAMES R. GARRETT, Assistant Examiner. 

